If Great Britain has cut ties to USA, has Canada? It would be expected that we would, but not enforceable. If Canada is anti-slavery have we accepted slave refugees?

Most of southern Canada and northern Mexico have been absorbed into the United States of North America. Canadians in particular tend to be a bit suspect, because there was a great deal of resistance to the unification process. (There was resistance in Mexico as well, but the ruling Mexican government at the time was pretty effective at squashing it.) It's fairly common for Canadians who've moved south of the old border to overcompensate in order to demonstrate their loyalty by doing things like owning more slaves than they really need.